10-57 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} \omega_i&=40.0\ut{rad/s}\\ \Delta t&=20.0\ut{s}\\ \omega_f&=0\\ \end{cases} $$ $$\ab{a}$$ $$\omega=\omega_0+\alpha t,$$ $$ \begin{aligned} \alpha&=\frac{\omega_f-\omega_i}{t}\\ &=2.00\ut{rad/s^2} \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} \Delta \theta&=\frac{1}{2}\(\omega_f+\omega_i\)t,\\ &=4.00\times10^2\ut{rad}\\ \end{aligned} $$ $$\ab{c}$$ $$ \begin{aligned} \Delta \theta&=4.00\times10^2\ut{rad}\\ &=(4.00\times10^2\ut{rad})\cdot\frac{1\ut{rev}}{2\pi\ut{rad}}\\ &=\frac{200}{\pi}\ut{rev}\\ &\approx 63.66197723675814\ut{rev}\\ &\approx 63.7\ut{rev}\\ \end{aligned} $$